1. Field of the Invention
The present invention relates to a package for housing a semiconductor element and more particularly to a package for housing a semiconductor element which is designed to prevent adverse effects of power supply noise on the semiconductor element housed therein.
2. Description of the Related Art
A conventional package for housing a semiconductor element usually comprises an insulating substrate which is composed of aluminum oxide sinter and has a semiconductor element-mounting section for mounting a semiconductor element at a top surface thereof and metallized wiring layers composed of powder of a high-melting point metal such as tungsten, molybdenum or manganese which lead out at positions from the periphery of the semiconductor element-mounting section to the outer regions of the insulating substrate; outer lead terminals attached to the metallized wiring layers by means of a soldering material such as silver solder for establishing connections between the respective electrodes of the semiconductor element and exterior electrical circuits; and a lid. The package for housing a semiconductor element is fabricated as a semiconductor device product by securely bonding the semiconductor element to the semiconductor element-mounting section of the insulating substrate by means of an adhesive such as glass, resin or soldering material while electrically connecting the respective electrodes to the metallized wiring layers by means of bonding wires, and then hermetically sealing the semiconductor element inside a container composed of the insulating substrate and the lid.
Here, this type of conventional package for a semiconductor element is constructed in such a manner that connection pads, which are connected to the power supply electrode and the grounding electrode of the semiconductor element to be housed therein, are formed on the top surface of the insulating substrate, electrodes of a capacitor element comprising barium titanate porcelain as a dielectric substance are attached to the connection pads by means of a soldering material such as solder, with the capacitor element located at some point along the connection between the power supply electrode and the grounding electrode of the semiconductor element, thereby effectively preventing the adverse effects of power supply noise on the semiconductor element.
However, since the connection pads provided on the insulating substrate are attached to the capacitor element by means of a solder in this type of conventional package for housing a semiconductor element and the melting point of the solder is as low as approximately 180.degree. C., the connection pads are detached from the capacitor element due to the heat of the fellow solder at as a high temperature as approximately 250.degree. C. when the semiconductor element is hermetically housed inside the package to fabricate a semiconductor device which is then connected to a wiring conductor of an exterior electrical circuit board by means of fellow solder. As a result, the package has a drawback in that the semiconductor element housed inside the package cannot be protected against the power supply noise and thus the semiconductor element cannot be operated under steady and normal conditions.
As a solution to overcome the drawback, it may be proposed to attach the capacitor element to the connection pads of the container by means of a high-melting point soldering material.
In cases where the soldering material for attaching the electrodes of the capacitor element to the connection pads of the container has a high melting point, there is presented a drawback in that the dielectric surface of the capacitor element is reduced to a metal by the heat applied when the electrodes of the capacitor element are attached to the connection pads of the container, and this causes a change in the capacity of the capacitor element and formation of a short circuit between the electrodes of the capacitor element, thereby making it impossible for the capacitor element to completely prevent the adverse effects of power supply noise on the semiconductor element for steady and normal operation of the semiconductor element over a long period of time.